1. Field of the Invention
The present invention relates to a method intended for real-time estimation of the instantaneous engine speed produced by each cylinder of an internal-combustion engine from the instantaneous speed detector located at the end of the transmission system.
2. Description of the Prior Art
Knowledge of the instantaneous speed for each cylinder allows estimation of the mean torque produced by each cylinder.
Estimation of the mean torque produced by each cylinder is important for all vehicles, whether equipped with gasoline or diesel engines. In the first case, it conditions good combustion of the mixture when the fuel/air ratio is close to 1, and therefore sensitive to cylinder to cylinder difference problems. In the second case, the knowing the torque allows readjustment so as to obtain optimum running conditions. Catalysts using a NOx trap lose efficiency in the course of time. In order to recover optimum efficiency, the torque of each cylinder has to be kept identical for some seconds, prior to returning to normal running conditions with a lean mixture. Removing pollution with DeNox catalysis therefore requires precise control of the torque cylinder by cylinder.
An instantaneous engine speed detector is therefore arranged at the end of the transmission system. This measurement is greatly distorted by the transmission and is affected by noise.
In order to control more precisely, and in particular individually, injection of the fuel masses into the cylinders, reconstruction of the torque cylinder to cylinder is necessary. Installing a digital torquemeter below each cylinder of a vehicle cannot be done considering the cost price thereof.
The method according to the invention provides an estimator, working from the measurement performed at the end of the transmission chain, to estimate the instantaneous engine speed below each cylinder.